Androgen receptor amplification is concordant between circulating tumor cells and biopsies from men undergoing treatment for metastatic castration resistant prostate cancer.

Increased activity has been shown to be preserved in spatially distinct metastatic tumors from the same patient suggesting the requirement for lineage-specific dependencies for metastatic castration resistant prostate cancer (mCRPC). Amplification of the gene is a common mechanism by which mCRPC increase activity. To determine whether amplification in circulating tumor cells (CTC) could complement metastatic tissue biopsies in men undergoing treatment for mCRPC, we developed a novel two-step assay to isolate CTCs and subsequently analyzed amplification status in CTCs and matched biopsy tissue from the same patient by fluorescence hybridization (FISH). gene status in CTCs showed strong concordance with gene status in matched tissue samples in 24 of 25 patients (Correlation: 96%; Kappa: 0.83; Sensitivity: 100%, Specificity: 83%). Our work demonstrates that amplification is conserved between CTCs and biopsies and that CTCs can serve as non-invasive surrogate to document amplification in mCRPC.